During a recent subzero cold snap, I spent my Saturday evening in an unusual way -- driving through the back alleys of downtown Minneapolis, searching for homeless people to invite to the Salvation Army's Harbor Light shelter.

I rode in the van with Brian Robertson, Harbor Light's head of security, and Sgt. Maj. Robert Strawberry, a chaplain. They told me that Harbor Light houses between 400 and 500 people a night and serves as many as 2,000 free meals a day.

As we prowled through the dark, peering under overpasses and scouting out footprints in the snow, I asked, "How do you know where to go to find these homeless people?" Strawberry's matter-of-fact answer: "Because I used to be there myself."

Eighty percent of Harbor Light's staff -- from food service workers to "advocates" who counsel clients and "provide a shoulder to cry on" -- are former drug addicts or alcoholics, according to Envoy Bill Miller, the facility's executive director. "I try to fill the ranks as much as possible with people who've been through the war themselves," he said.

Strawberry, for example, joined the staff in 1994.

"I was an addict and a street-fighter," he said. "I have scars and two bullet wounds." He first showed up at Harbor Light because he heard he could get a free meal there, he says.

Robertson, who arrived in 2004, is also a former drug addict and alcoholic. "Everyone had given up on him," said Miller. "Now he's head of security, maintenance and housekeeping. I trust him with the whole building."

Then there's newcomer Michele Bradley, now employed as a client advocate. A former heroin and crack addict, she arrived in April from Pittsburgh, where she had repeatedly failed in her struggles to recover.

Harbor Light's goal is to prepare people for employment and independent living. It is the state's largest social-service provider, and offers a homeless shelter, chemical dependency treatment, and transitional and permanent housing, according to Miller.

The Salvation Army contracts with Hennepin County for many nonreligious aspects of its programs. It also offers services like BOLT (Basics of Life Training), which teaches the rudiments of financial management, healthy living and spiritual life.

Behind it all stands Miller, the son of a former Salvation Army national commander. Miller knows homelessness firsthand, having studied it by living on the streets for a month while earning his master's degree in social work at the University of Kentucky.

Harbor Light was floundering when Miller arrived in 2000. It was dangerous and disorderly, to the point that its contracts with the county were at risk. Miller astonished everyone by ripping out the fences, metal detectors and X-ray machines. "It was wall-to-wall negativity," he said, adding, "The police thought I was crazy."

Today, signs at Harbor Light are warm and welcoming. "Our mission statement is, 'treat everyone with respect and dignity, as you would like to be treated, and we won't have any problems,' " explained Miller.

Miller is widely loved, says Robertson. "This man can't walk 50 feet in this city without someone coming up and hugging him, thanking him for what he's done," he said.

Why do Harbor Light's programs work for many people? The answer, in two words, is hope and gratitude.

Hope is hard to come by when you're a repeat loser like Robertson, who thought addiction had him by the throat. "But at Harbor Light," he said, "our motto is 'You may be down, but you're never out.' "

Where does this hope come from? "The Bible says, 'God changes the hearts of kings,'" Robertson explained. "He softened my heart and transformed me. My gratitude knows no bounds. I know the sky's the limit for anyone who walks through that door and needs my help."

The fruit of this philosophy is on display at the 10 a.m. Sunday service at Harbor Light's chapel. The standing-room-only congregation ranges from homeless people sleeping it off in the corners to professionals in coats and ties. Most have struggled with addiction or have family members who have, says Miller.

The mood is so exuberant, the crowd so fervent, the gratitude so palpable, the gospel music so uplifting, that it's hard to sit still.

The Sunday I attended, Miller preached a sermon titled "Nobody's Perfect." It focused on the Old Testament story of Samson and Delilah. Samson gave in to temptation and was captured and mocked by his enemies. But he repented and, with God's help, triumphed in the end.

"What I got out of that story," said Robertson, "is that God gives you a way out. You admit you made mistakes, and God will forgive you when nobody else will."

There are many sinners at Harbor Light on Sunday morning. But the message they hear is transforming: "A saint is just a sinner who gets back up again."